The present invention is based on two fundamental premises: i) effectively curing malignancy such as cancer depends early detection, which has two elements: sufficient image resolution to identify small lesions and tumors, and sufficient and reliable viewing coverage to ensure there are no diagnostic blind spots; and ii) because viewing is limited, current endoscopic diagnostic procedures can be time consuming and require substantial training. For example, the main challenge in cystoscopic screening of bladder cancer is ensuring that the diagnosis reliably covers the entire interior bladder surface.
Being able to obtain high-resolution wide-angle endoscopic maps would be useful in diagnosis, surgical planning, surgical intervention, and post-surgical diagnosis for verifying tumor removal. Particular utility would be in cystoscopic cancer screening, hysteroscopic diagnosis of the interior surface of the uterus (National Institute of Health Grant No. 1R43CA097824-01), imaging of the nose and throat cavities, and neuroendoscopy of the brain's ventricular system where it is very easy to get disoriented and where it is important to minimize gross instrument motion. Further applications include arthroscopy for imaging of joint cavities, and endoscopic inspection of the thorax.
Current technology is limited in its ability to provide both high resolution and wide reliable viewing coverage in a single system. Noninvasive imaging techniques such as X-ray, MRI, CT, ultrasound, and their derivative virtual endoscopy, have unlimited viewing directionality and the positioning accuracy necessary for building complete diagnostic maps of the anatomy, but their imaging resolution is an order of magnitude less than that of endoscopy. Currently these methods are only able to resolve mature tumors several millimeters in diameter, and improving this resolution is still going to require prolonged scientific development. It is also unlikely that these techniques will ever be able to identify tissue color, which is important in diagnosis.
Conversely, endoscopic imaging has excellent optical resolution and color information but is plagued by inconsistencies in viewing coverage. The endoscopic viewing process is hampered by a limited field of view and is mechanically constrained by the endoscope insertion port and interior anatomy. It is further complicated by the fact that the endoscope provides no natural sense of orientation, and it is common for an operator to get lost or disoriented while using endoscopes. Getting reliable diagnoses with endoscopes is therefore operator dependent, and there is great variability in the skill levels of endoscopists. Obtaining a structured sense of the surroundings requires the endoscopist to cover all areas of an inspection site and to keep a mental record of the relative endoscopic viewing positions. It also requires that the endoscopist distinguish between regions already covered and regions not yet inspected (much like to trying to ensure complete coverage when vacuuming the floor). These tasks require great technical skill, spatial awareness, and memory and are so challenging that endoscopic diagnoses often leave missed areas.
One of the underlying problems here is that endoscopic diagnosis is generally a free-hand technique. Whether the diagnosis is being performed with a fixed-angle endoscope, a flexible variable direction of view scope (U.S. Pat. No. 3,880,148 to Kanehira, U.S. Pat. No. 5,257,618 to Kondo), or a rigid variable direction of view scope (U.S. Pat. No. 3,856,000 to Chikama, U.S. Pat. No. 4,697,577 to Forkner, U.S. Pat. No. 6,371,909 to H.o slashed.eg et al., U.S. Pat. No. 6,364,830 to Durell, U.S. Pat. No. 6,500,115 to Krattiger et al.), or a hybrid scope, (the LTF TYPE V3 Olympus Laparo-Thoraco Videoendoscope in which the main shaft is rigid but the tip portion can be flexed), it is subject to the inconsistencies of manual endoscope manipulation with no means for doing accurate position registration between views. The VOCAL (Video Optical Comparison and Logging) software package somewhat improves this situation by recording running video of endoscopic procedures and integrating sequential frames into composite images. This provides the user with a broader diagnostic overview but does not address the problem of discontinuous coverage and missed areas and also does not yield accurate information about the relative location of viewed areas.
Other attempts to minimize diagnostic inconsistencies are disclosed in U.S. Pat. No. 5,313,306 to Kuban et al., U.S. Pat. No. 6,449,103 to Charles, and U.S. Pat. No. 5,800,341 to McKenna et al. These designs propose to capture panoramic or omniramic imaging information in a single large frame and avoid the problem of having to mentally patch together disjoint view fields. While good in concept, these designs can not currently provide sufficient resolution and illumination and have apparently never been reduced to practice.
Accordingly, the current invention provides a method for capturing composite endoscopic images. This method will improve endoscopic diagnosis by providing accurate high-resolution low-distortion wide-angle visual coverage; obtaining panoramic and omniramic information by automated capture; building and displaying composite images of the endoscopic space with minimal blind spots; minimizing user disorientation; and reducing procedure time. Other advantages will become apparent from the following.